Search results for "Chemical"

Historia de las madres en occidente: repensar la maternidad

2005

El objetivo del presente trabajo es profundizar sobre la historia de la concepción de la maternidad, enmarcándola como un proceso evolutivo y vital propio del desarrollo psicobiológico humano, pero con características diferentes en cada etapa histórica. Ser madre en la especie humana excede el hecho biológico y tiene un significado a nivel social, cultural, histórico y psicológico. Dos fenómenos han influído fuertemente a partir de la segunda mitad del Siglo XX - en la historia de la maternidad: los estados de bienestar,-especialmente en los países desarrollados- y el crecimiento de las ciencias biológicas en relación a la posibilidad a planificar los nacimientos. La maternidad recorre el c…

La palabra en las maternidades: una aproximación a la psicología perinatal

2001

El reconocimiento del recién nacido como un ser interactuante con el medio físico y humano que lo rodea, implicó cambios en las conductas de los equipos de salud , a cargo de las unidades de internación neonatal. Los conceptos de interacciones precoces, de apego, de díada, de vulnerabilidad maternal, competencias conductuales del recien nacido, y su utilización reciente en el desarrollo de la psicología perinatal, marcaron una transformación en el enfoque de los distintos profesionales involucrados en el proceso del nacimiento. Por un lado, podemos decir que la medicalización del acto del nacimiento en la sociedad occidental ha permitido disminuír el riesgo morbi-mortalidad matern…

Spin filtering by proximity effects at hybridized interfaces in spin-valves with 2D graphene barriers

2020

We report on spin transport in state-of-the-art epitaxial monolayer graphene based 2D-magnetic tunnel junctions (2D-MTJs). In our measurements, supported by ab-initio calculations, the strength of interaction between ferromagnetic electrodes and graphene monolayers is shown to fundamentally control the resulting spin signal. In particular, by switching the graphene/ferromagnet interaction, spin transport reveals magneto-resistance signal MR > 80% in junctions with low resistance × area products. Descriptions based only on a simple K-point filtering picture (i.e. MR increase with the number of layers) are not sufficient to predict the behavior of our devices. We emphasize that hybridization …

Hexakis(diethylacetamide)iron(II) hexahalorhenate(IV) ionic salts: X-ray structures and magnetic properties

2015

Two novel Fe<sup>II</sup>-Re<sup>IV</sup> compounds of general formula [Fe<sup>II</sup>(DEA)<inf>6</inf>][Re<sup>IV</sup>X<inf>6</inf>] where DEA = diethylacetamide and X = Cl (1) and Br (2) have been prepared and magnetostructurally characterised. Complexes 1 and 2 are isomorphic ionic salts that crystallise in the trigonal crystal system with space group R(-3). The rhenium(IV) ion in 1 and 2 is six-coordinate with six chloro (1) or bromo (2) ligands building a regular octahedral chromophore. The Fe<sup>II</sup> ion is also six-coordinate, and bonded to six oxygen atoms from six DEA molecules. [Fe<sup&gt…

Use of Density Functional Based Tight Binding Methods in Vibrational Circular Dichroism.

2018

Vibrational circular dichroism (VCD) is a spectroscopic technique used to resolve the absolute configuration of chiral systems. Obtaining a theoretical VCD spectrum requires computing atomic polar and axial tensors on top of the computationally demanding construction of the force constant matrix. In this study we evaluated a VCD model in which all necessary quantities are obtained with density functional based tight binding (DFTB) theory. The analyzed DFTB parametrizations fail at providing accurate vibrational frequencies and electric dipole gradients but yield reasonable normal modes at a fraction of the computational cost of density functional theory (DFT). Thus, by applying DFTB in comp…

“Sweet” ionic liquid gels: materials for sweetening of fuels

2018

The search for new materials to be used in desulfurisation (sweetening) of fuels is one of the main topics of current research. In this paper, we explored the possibility of using supramolecular gels obtained from the gelation of ionic liquid binary mixtures. Indeed, some ionic liquids are generally known as efficient extraction phases for desulfurisation of fuels. In rare cases, one of their main drawbacks is their partial solubility in the fuel, leading to contamination. Then, their immobilisation due to the formation of a gelatinous network may be a challenge. Ionic liquid gels were obtained by mixing certain [NTf2]−-based ionic liquids (solvents) with the ones of gluconate-based ionic l…

Injection and ultrafast regeneration in dye-sensitized solar cells

2014

Injection of an electron from the excited dye molecule to the semiconductor is the initial charge separation step in dye-sensitized solar cells (DSC's). Though the dynamics of the forward injection process has been widely studied, the results reported so far are controversial, especially for complete DSC's. In this work, the electron injection in titanium dioxide (TiO2) films sensitized with ruthenium bipyridyl dyes N3 and N719 was studied both in neat solvent and in a typical iodide/triiodide (I-/I3 -) DSC electrolyte. Transient absorption (TA) spectroscopy was used to monitor both the formation of the oxidized dye and the arrival of injected electrons to the conduction band of TiO2. Emiss…

Hard cap espresso extraction and liquid chromatography determination of bioactive compounds in vegetables and spices

2017

Abstract A new analytical procedure, based on liquid chromatography with diode array and fluorescence detection, has been proposed for the determination of bioactive compounds in vegetables and spices after hard cap espresso extraction. This novel extraction system has been tested for the determination of capsaicin and dihydrocapsaicin from fresh chilli and sweet pepper, piperine from ground pepper, curcumin from turmeric and curry, and myristicin from nutmeg. Extraction efficiency was evaluated by using acetonitrile:water and ethanol:water mixtures. The proposed method allows the extraction of samples with 100 mL of 60% (v/v) ethanol in water. The obtained limits of quantification for the …

Characteristic asymptotics for fast chemical reaction

1995

Removing the saturation assumption in Bank-Weiser error estimator analysis in dimension three

2020

International audience; We provide a new argument proving the reliability of the Bank-Weiser estimator for Lagrange piecewise linear finite elements in both dimension two and three. The extension to dimension three constitutes the main novelty of our study. In addition, we present a numerical comparison of the Bank-Weiser and residual estimators for a three-dimensional test case.